1、新建模块：spring-boot-websocker
添加pom依赖：
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-websocket</artifactId></dependency>

2、建包：config、controller
WebSocketConfig
/**

• WebSocket的配置类

• 开启了WebSocket支持
  */
  @Configuration
  public class WebSocketConfig {

  @Bean
  public ServerEndpointExporter serverEndpointExporter() {
  return new ServerEndpointExporter();
  }

}

WebSocketServer
//客户端向服务器端建立WebSocket连接的url
@ServerEndpoint("/websocket")
@Component
public class WebSocketServer {

//静态变量，用来记录当前在线连接数,可选
private static int onlineCount = 0;

//concurrent包的线程安全Set，用来存放每个客户端对应的MyWebSocket对象，必须
private static CopyOnWriteArraySet<WebSocketServer> webSocketSet
        = new CopyOnWriteArraySet<WebSocketServer>();

//与某个客户端的连接会话，需要通过它来给客户端发送数据,必须
private Session session;


/**
 * 连接建立成功调用的方法
 */
@OnOpen
public void onOpen(Session session) {
    this.session = session;
    webSocketSet.add(this);     //将客户端加入set中
    addOnlineCount();           //在线数加1
    System.out.println("有新窗口开始监听,当前在线人数为"
            + getOnlineCount());
    try {
        sendMessage("连接成功");
    } catch (IOException e) {
        System.out.println("WebSocket IO异常");
    }
}

/**
 * 连接关闭调用的方法
 */
@OnClose
public void onClose() {
    webSocketSet.remove(this);  //从set中删除
    subOnlineCount();           //在线数减1
    System.out.println("有连接关闭！当前在线人数为" + getOnlineCount());
}

/**
 * 收到客户端消息后调用的方法
 *
 * @param message 客户端发送过来的消息
 */
@OnMessage
public void onMessage(String message, Session session) {
    System.out.println("收到客户端的信息:" + message);
    //群发消息
    for (WebSocketServer item : webSocketSet) {
        try {
            item.sendMessage(message);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

/**
 * @param session
 * @param error
 */
@OnError
public void onError(Session session, Throwable error) {
    System.out.println("发生错误");
    error.printStackTrace();
}

/**
 * 实现服务器主动推送
 */
public void sendMessage(String message) throws IOException {
    this.session.getBasicRemote().sendText(message);
}


/**
 * 群发自定义消息
 */
public static void sendInfo(String message) throws IOException {
    System.out.println("推送消息内容:" + message);
    for (WebSocketServer item : webSocketSet) {
        try {
            item.sendMessage(message);
        } catch (IOException e) {
            continue;
        }
    }
}

public static synchronized int getOnlineCount() {
    return onlineCount;
}

public static synchronized void addOnlineCount() {
    WebSocketServer.onlineCount++;
}

public static synchronized void subOnlineCount() {
    WebSocketServer.onlineCount--;
}

}

WebSocketController
@RestController
public class WebSocketController {

//推送数据接口
@GetMapping("/socket/push")
public String pushMsg(String message) {
    try {
        WebSocketServer.sendInfo(message);
    } catch (IOException e) {
        e.printStackTrace();
    }
    return "success";
}

}

测试swagger